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Large portions of Arizona and western New Mexico are forecast to have above-normal significant fire potential now through August, according to a report released May 1.
"In 2012, the Southwest has experienced fires in excess of 12,000 acres, which is less than half of what the area experienced by this time last year," said Gregg Garfin, assistant professor in the University of Arizona's School of Natural Resources and the Environment and deputy director for science translation and outreach at the Institute of the Environment.
"Nevertheless, fuel moistures across the Southwest are in the lowest 10 percent of historic values, observed fire danger is high to very high, and forecast fire danger is very high to extreme. We already have notices of fire restrictions in Arizona's Coconino and Tonto national forests, in the Fossil Creek area. With continued dry conditions, we can expect further notices of fire restrictions and closures on public lands," said Garfin, who participated in the report's forecast discussions.
Residents living where wildlands and urban areas meet can still take measures to reduce the risk of fires impacting their homes by clearing dried vegetation from their properties, he added.
Significant fire potential refers to the likelihood that a wildland fire will require additional resources from outside the area in which the fire originated.
Areas designated "above normal" are likely to require additional external resources during the forecast period.
Above-normal potential is expected through August in mountain areas in Arizona and western New Mexico, although experts' confidence in the forecast is low. The expected shift in Pacific Ocean conditions, out of La Niña, which is associated with dry winters and springs in the Southwest, toward neutral or El Niño conditions, which tend to bring wet winters and springs to the region, increases the chances of precipitation in the region.
"The rate at which these transitions occur is difficult to predict-a real wild card," Garfin said.
Worsening drought conditions, forecasts of periods of abnormal heat and dryness, and drier-than-normal heavier fuels such as trees, standing dead stems and downed tree limbs in higher elevations contributed to the Southwest fire outlook. The dryness of these fuels increases flammability and the likelihood of fire spreading rapidly.
"Though parts of the Southwest received ample precipitation in late 2011, the decaying La Niña episode, which began in 2010, turned off the precipitation tap to the region since the beginning of 2012," said Garfin, also an investigator for the Climate Assessment for the Southwest project, or CLIMAS.
"In the last six months most of Arizona has received less than 70 percent of average precipitation, with many weather stations reporting less than 50 percent of average. Northern New Mexico also has been exceedingly dry."
In addition, with forecasters expecting fewer gusty conditions, significant fire activity is more likely to occur in terrain with wide variations in topography, where fire can spread upslope in heavier, dry fuels, and where it is more difficult to attack fires from the ground, Garfin said.
Normal significant fire potential is forecast for other parts of Arizona and New Mexico.
Such details came out of the 2012 National Seasonal Assessment Workshop Report for the Western States, Alaska and Hawaii, which was drafted by fire, weather and climate specialists from state and federal agencies, in discussion with experts from the UA and other universities.
The outlook is based primarily on interactions among climate factors, fuel types and conditions, long-range predictions for climate and fire and the persistence of disturbance factors, such as drought and insect-induced forest mortality.
The workshop was part of the 10th national assessment organized by CLIMAS, the Predictive Services Interagency Group and the Program for Climate, Ecosystem and Fire Applications at the Desert Research Institute.
Elsewhere in the West, above-normal significant fire potential is forecast from June through August in the Rocky Mountains and portions of western Colorado and south-central Wyoming. Other areas with similar fire potential likely will stretch from the mountains in Southern California northward across western Nevada and into southeastern Oregon and southwest Idaho in July and August.